Citotoxicidade de soldas elétricas a ponto: estudo in vitro / Cytotoxicity of electric spot welding: an in vitro study

OBJETIVO: o processo de solda envolve íons metálicos capazes de provocar lise celular. Diante disso, o objetivo deste estudo foi testar a hipótese de que existe citotoxicidade entre diferentes tipos de ligas (CrNi, TMA, NiTi) utilizadas em Ortodontia, submetidas à solda elétrica a ponto. MÉTODOS: três tipos de ligas foram avaliados neste estudo. Foram confeccionados 36 corpos de prova, 6 para cada combinação entre os fios, divididos em 6 grupos - grupo AA (aço com aço), grupo AT (aço com TMA), grupo AN (aço com NiTi), grupo TT (TMA com TMA), grupo TN (TMA com NiTi) e grupo NN (NiTi com NiTi) - que foram submetidos à solda a ponto para avaliação quanto ao possível efeito citotóxico nos tecidos bucais. Previamente, os corpos de prova foram limpos com álcool isopropílico e esterilizados em luz ultravioleta. O ensaio de citotoxicidade foi realizado utilizando-se cultura de células (linhagem L929, fibroblastos de camundongos), submetida ao teste para células viáveis em vermelho neutro ("dye-uptake") no tempo de 24h. A análise de variância e comparação múltipla (ANOVA) e teste de Tukey foram utilizados (p< 0,05). RESULTADOS: os resultados demonstraram que não houve diferença estatisticamente significativa entre os grupos experimentais (P> 0,05). Foi observada maior viabilidade celular no grupo TT, seguido dos grupos AT, TN, AA, NA e NN. CONCLUSÃO: pôde-se evidenciar que solda em fios de liga de NiTi causaram maior quantidade de lise celular. Soldas elétricas a ponto demonstraram pequena capacidade de causar lise celular.

OBJECTIVE: The welding process involves metal ions capable of causing cell lysis. In view of this fact, the aim of this study was to test the hypothesis that cytotoxicity is present in different types of alloys (CrNi, TMA, NiTi) commonly used in orthodontic practice when these alloys are subjected to electric spot welding. METHODS: Three types of alloys were evaluated in this study. Thirty-six test specimens were fabricated, 6 for each wire combination, and divided into 6 groups: Group SS (stainless steel), Group ST (steel with TMA), Group SN (steel with NiTi), Group TT (TMA with TMA), Group TN group (TMA with NiTi) and Group NN (NiTi with NiTi). All groups were subjected to spot welding and assessed in terms of their potential cytotoxicity to oral tissues. The specimens were first cleaned with isopropyl alcohol and sterilized with ultraviolet light (UV). A cytotoxicity assay was performed using cultured cells (strain L929, mouse fibroblast cells), which were tested for viable cells in neutral red dye-uptake over 24 hours. Analysis of variance and multiple comparison (ANOVA), as well as Tukey test were employed (p<0.05). RESULTS: The results showed no statistically significant difference between experimental groups (P>0.05). Cell viability was higher in the TT group, followed by groups ST, TN, SS, NS and NN. CONCLUSIONS: It became evident that the welding of NiTi alloy wires caused a greater amount of cell lysis. Electric spot welding was found to cause little cell lysis.

Effect of temperature variation on the cytotoxicity of cast dental alloys and commercially pure titanium

Cell culture system has been used to evaluate alloy cytotoxicity under different environments, testing the extracts, but the effect of temperature variation on the cytotoxicity of dental alloys has not been analyzed. OBJECTIVE: The aim of the present study was to investigate if temperature variation could affect dental alloy cytotoxicity, testing alloy extracts in an epithelial cell culture system. MATERIAL AND METHODS: Discs of Ni-Cr, Co-Cr-Mo, Ni-Cr-Ti, Ti-6Al-4V and commercially pure titanium (cp Ti) were cast by arc melting, under argon atmosphere, injected by vacuum-pressure. Discs were immersed in artificial saliva and subjected to different temperatures: 37ºC and thermocycling (37ºC/5ºC/37ºC/55ºC/37ºC). After thermocycling, extracts were put in a subconfluent culture during 6 h, and the number of cells and their viability were used to evaluate cytotoxicity in these temperatures. For each alloy, data from temperature conditions were compared by Student's t-test (α=0.05). RESULTS: The cytotoxicity tests with alloy/metal extracts showed that Ni-Cr, Co-Cr-Mo, Ti-6Al-4V and cp Ti extracts (p>0.05) did not affect cell number or cell viability, while Ni-Cr-Ti (p<0.05) extract decreased cell number and viability when the alloy was subjected to thermocycling. CONCLUSION: Within the limitations of the present study, the Ni-Cr-Ti alloy had cell number and viability decreased when subjected to temperature variation, while the other alloys/metal extracts did not show these results.

[Invitro evaluation of cytotoxicity and elemental release of three types of nickel-chromium basemetal alloys and comparison with one type of high noble [gold-palladium-silver] alloy]

Dental alloys following corrosion cause changes in oral tissues. As base metal alloys are used for fabrication of dental prostheses and are manufactured in Iran, the aim of this study was to investigate the cytotoxicity of three types of nickel-chromium base metal alloys with one type of high noble alloy on mouse fibroblast cell [L 929] by MTT test. In this experimental study, 12 disks of each alloy with 5mm diameter and 2.5 mm thickness were prepared and placed in RPMI culture medium for 48 hours and 72 hours [extract medium]. Then the extract mediums were diluted in two different dilutions of 200 micro 1 and 40 micro 1 and their cytotoxicity were evaluated by MTT assay and compared with two control groups consist of only culture media and culture media with teflon. The amount of Nickel, chromium, copper, zinc and silver released from each alloys were measured by flame atomic absorption device. The data were analyzed by Graph Instat software, one way ANOVA and Tukey tests. After 48 hours, no significant difference in cytotoxicity was found between samples and control groups. After 72 hours there was a significant difference between samples and control groups [Minalux vs. Control: P<0.01, Degubond vs. Control: P<0.001, Wiron 99 vs. Control: P<0.001, Supercast vs. Control: P<0.05] There was no significant difference in cytotoxicity with two dilutions of 200 micro 1 and 40 micro 1 between samples. Maximum release of nickel and chromium were observed from Minalux, silver from Degubond and zinc Supercast. The cytotoxicity of three Nickel-Chromium alloys and one high noble which were used in this study was not different. Cytotoxicity increased with time

Ligas para amálgama contendo zinco: quando devemos usá-las? / Dental amalgam alloy containing zinc: when should we use them?

O presente estudo teve por objetivo avaliar, por revisäo da literatura, o efeito da inclusäo do zinco nas ligas de amálgama dentário. Para isso, foram analisadas a microestrutura, as propriedades físicas, a corrosäo, a deterioraçäo, fraturas marginais e a citoxicidade do amálgama

Amalgama Dental: revisión de la Literatura y Estado Actual / Dental Amalgam: literature review and current concepts

Este artículo presenta el desarrollo de las aleaciones modernas de amalgama, su comportamiento clínico de acuerdo a su composición y su forma física y la apropiada manipulación de estos materiales. Se concluye con una breve discusión de las restauraciones adhesivas de amalgama, y una observación acerca del potencial tóxico de mercurio en la amalgama